This invention relates to patient ventilator systems in which breathing gas is circulated through a carbon dioxide absorber canister, and more particularly, to an improved carbon dioxide absorber canister having an integral moisture sump.
In ventilator systems designed to provide respiratory gases to patients, condensation of water vapor commonly occurs in breathing circuit components due to the high humidity of patients"" expired gases. Breathing circuits of the re-circulatory type include a carbon dioxide absorbing canister. Condensate is especially troublesome in carbon dioxide absorbing canisters and associated tubing and valves and may interfere with proper operation of the canisters and breathing circuit. When a patient requires prolonged use of a ventilator system, substantial condensate can accumulate, requiring medical personnel attending the patient to periodically rid the ventilator system of the excessive moisture.
Prior art ventilator systems have utilized various sumps to trap and remove condensate. The carbon dioxide absorbing canister itself has often been relied on as a common sump although the canister""s primary function is removing carbon dioxide from the patient""s expired breathing gases.
However, there exist areas in the breathing circuit that are difficult to drain to the carbon dioxide absorber canister. For example, the canister inlet structure, located upstream of the canister itself, including the expiratory check valve of the breathing system, is inherently difficult to maintain free of excessive condensate. In prior systems, the periodic actuation of a valve by a patient attendee was necessary for removal of condensate in this area.
Alternatively, separate stand-alone sumps have been employed specifically to drain the moisture from problematic areas. These sumps allowed the patient""s attendees to view the collected moisture through a window or a transparent container so that the attendee could empty the collected moisture before the sump overflowed into the breathing circuit.
In practice, both the valve actuation mechanisms and the stand alone sump arrangements require extensive vigilance on the part of the patient""s attendees. This demand on the attendees only adds to the already numerous ventilator servicing requirements which include removing and replacing spent carbon dioxide absorbing materials from the canister, ensuring proper composition of ventilator gases, maintaining desired gas volumes and pressures in the breathing circuit, and maintaining optimum humidity in inspiratory breathing gases. These varied tasks create multiple opportunities for operating errors to occur.
Therefore, an approach that avoids the above-described condensate-related problems and reduces condensate buildup problems in hard to drain breathing circuit areas, while simultaneously lowering the demands on the patient attendees, is highly desirable.
This invention is a carbon dioxide absorber canister with an integral moisture sump. The moisture sump collects condensate from areas of a breathing circuit that are difficult to drain to a common sump, such as the carbon dioxide absorber canister itself. The moisture sump found in the present invention may be integrally formed into the structure of the carbon dioxide absorber canister, the canister including a hollow container adapted to contain a carbon dioxide absorbing material.
The moisture sump includes a reservoir chamber for accepting collected condensate. The reservoir chamber may be arcuately-shaped with an upwardly facing entrance formed by surrounding walls. The entrance to the reservoir chamber offers a sealing surface for pneumatically sealing with the breathing circuit. This pneumatic seal is arranged so that the seal is accomplished by attachment of the carbon dioxide absorber canister to the patient ventilator system and is broken when the canister is subsequently removed from the system.
The moisture sump is adapted to collect condensate from breathing circuit areas proximate the inlet and outlet ports of the canister. Such areas include the inlet structures and outlet structures located in the patient ventilator system, specifically, the expiratory check valve and the inspiratory check valve. As noted above, the expiratory check valve is known to be a particularly troublesome area from which to drain condensed moisture.
The moisture sump""s reservoir chamber may have a volume sized to accommodate the maximum amount of condensate collected in a given time interval, such as the life expectancy of the carbon dioxide absorbing material contained within the hollow container of the canister. Therefore, the patient""s attendees are not required to monitor the moisture buildup in the moisture sump independently of other tasks. Removal of the carbon dioxide absorber canister from the breathing circuit automatically ensures that the condensed moisture contained in the integral sump is also removed.